Plastering and brickwork pathologies: Which of the following statements are correct?

Introduction / Context:
Post-construction surface defects are common in masonry and plaster finishes. Recognizing typical symptoms and remedies allows effective maintenance and avoids misdiagnosis that can lead to inappropriate repairs.

Given Data / Assumptions:

• Plastered masonry walls with normal environmental exposure.
• Efflorescence arises from soluble salts migrating to the surface.
• Thermal and moisture movements can induce cracking or debonding.

Concept / Approach:
Hair cracks (crazing or fine shrinkage cracks) are frequently observed due to drying shrinkage, inadequate curing, or minor substrate movement. Efflorescence results from evaporation leaving salt crystals; mild efflorescence may be treated with brushing and solutions like zinc sulphate to neutralize and remove deposits. Large thermal gradients can cause differential movement between plaster and backing, weakening the bond and leading to drumming or fall-off.

Step-by-Step Solution:
Assess (a): hairline cracks on plaster → common and well-documented.Assess (b): zinc sulphate solution is a known treatment to help remove efflorescence and reduce reappearance.Assess (c): excessive thermal variation causes expansion/contraction mismatch → potential debonding and failure.Therefore choose “All of the above”.

Verification / Alternative check:
Maintenance manuals recommend mechanical removal plus chemical washes for efflorescence, and control joints/cures for shrinkage cracking; thermal protection and shading reduce debonding risks.

Why Other Options Are Wrong:
Selecting only some statements ignores well-known causes and remedies in building pathology.

Common Pitfalls:
Painting over efflorescence without removal; neglecting curing; omitting movement joints or thermal considerations in exposed walls.

Final Answer:
All of the above.